Imaging systems capture two dimensional information regarding electromagnetic radiation that is emitted by objects in a designated region of the infrared spectrum over a field of view. Typically the two dimensional information is captured at a focal plane that is perpendicular to the optical axis of a focusing lens or mirror and passes through the focal point of the lens or mirror. Techniques have been developed to display the information at the focal plane in a visible spectrum in a manner that indicates comparative levels of infrared emission intensity across the focal plane. Because warmer objects radiate more infrared radiation and cooler objects radiate less infrared radiation, the displayed images provide an indication of the comparative temperature of objects in the field of view.
Imaging technology, and particularly infrared imaging technology has developed very rapidly, particularly since the widespread acceptance of uncooled focal plane array detectors. Imagers are now capable of detecting faulty steam traps, leaking hydrocarbon gases, water leaks in roofing, inadequate building insulation, effect of friction from various causes, electrical faults, heat exchanger faults, fluid levels, etc. Problems and other findings may be detected by a skilled in-field operator using a modern infrared camera appropriate to the task. Another important development has been the integration of computational systems, digital displays, and versatile user interaction devices into handheld or otherwise portable infrared imaging systems like those disclosed Piety in U.S. Pat. No. 5,386,117 (referred to hereinafter as '117), Warner in U.S. Pat. No. 6,849,849 (referred to hereinafter as '849), Hamrelius in U.S. Pat. No. 6,984,824 (referred to hereinafter as '824), and Garvey in US Patent Application Publication US 20060017821 (referred to hereinafter as 20060017821). However, there are problems with existing technology. These problems include:                Detection and documentation of one or more of the cited problems result in an incomplete in-field solution.        Set-up requirements to adequately interpret the signal are too complex or require a higher level of end user knowledge.        Manually configured evaluation parameters cannot be readily adapted to changing conditions in the monitored asset.        Inadequate methods to automatically compare current readings with previous measured or stored readings.        Inability to monitor an asset and detect significant variations from previous measurements in an automated fashion.        
What are needed are devices and methods for determining a performance characteristic associated with an object having an intended function.